The BIOS of the P4S800D is based on the AMI microcode and thus resembles the BIOSes of the P4P800 series mainboards. However, SiS655FX chipset brought certain changes, mostly into the page where you configure the memory subsystem.
Other mainboards may envy the flexibility offered by this BIOS Setup. Moreover, all these parameters affect seriously the performance of the system and it took me quite a while to set the P4S800D up for maximum performance (you see the options I used in the tests in the screenshot). When set to “MA 1T”, the MA 1T/2T Select parameter allows increasing the performance even higher, but the system becomes unacceptably unstable in this case.
Hardware monitoring options of ASUS P4S800D allow tracking the temperatures of the CPU and the mainboard, the rotational speeds of three fans and four voltages. You receive the exclusive ASUS Probe utility with the mainboard, which monitors all those things from inside the Windows environment. The reviewed mainboard also boasts the ASUS exclusive feature called Q-Fan. This technology reduces the CPU cooler speed if the temperature inside the system case is within the acceptable range, thus reducing the noise.
The BIOS Setup of ASUS P4S800D is not rich in CPU overclocking options. Yes, you can change the FSB clock rate from 100 to 300MHz with 1MHz increment, but the control over voltages is insufficient: Vmem can be set to 2.55, 2.65, 2.75 and 2.85V; the Vagp is varied from 1.5V to 1.8V with 0.1V stepping; the Vcore can be only increased by 0.1V above the nominal value – this may be enough just for ordinary (non-extreme) overclocking as Pentium 4 processors are not very sensitive to the voltage they receive.
Thanks to the SiS655FX chipset, the frequencies of the AGP and PCI buses are locked at their normal values, 66/33MHz.
Our overclocking attempts with the ASUS P4S800D were a bit of a disappointment. The Pentium 4 2.4C processor that we used with this mainboard can speed up to 3.6GHz at 300MHz FSB, but we couldn’t repeat this result on the ASUS mainboard even reducing the memory clock rate to the minimum. It’s hard to tell certainly what was the reason, but the mainboard would lose stability at 255MHz FSB. Moreover, from 240MHz FSB on, you have to use specific memory modules as the system wouldn’t start up with some modules, irrespective of the FSB/MEM divisor, timings and the rated frequency of the modules.
So ASUS P4S800D mainboard can only be used for moderate overclocking. The basic disadvantage of this mainboard is its limited abilities in controlling the Vcore and low stability at the FSB frequency over 240-250MHz.